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[elogind.git] / man / sd_id128_get_machine.xml

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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+  This file is part of elogind.
+
+  Copyright 2012 Lennart Poettering
+
+  elogind is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  elogind is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with elogind; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_id128_get_machine">
+
+  <refentryinfo>
+    <title>sd_id128_get_machine</title>
+    <productname>elogind</productname>
+
+    <authorgroup>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Lennart</firstname>
+        <surname>Poettering</surname>
+        <email>lennart@poettering.net</email>
+      </author>
+    </authorgroup>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_id128_get_machine</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_id128_get_machine</refname>
+    <refname>sd_id128_get_boot</refname>
+    <refpurpose>Retrieve 128-bit IDs</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;elogind/sd-id128.h&gt;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>int <function>sd_id128_get_machine</function></funcdef>
+        <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_id128_get_boot</function></funcdef>
+        <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_id128_get_machine()</function> returns the
+    machine ID of the executing host. This reads and parses the
+    <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+    file. This function caches the machine ID internally to make
+    retrieving the machine ID a cheap operation.</para>
+
+    <para><function>sd_id128_get_boot()</function> returns the boot ID
+    of the executing kernel. This reads and parses the
+    <filename>/proc/sys/kernel/random/boot_id</filename> file exposed
+    by the kernel. It is randomly generated early at boot and is
+    unique for every running kernel instance. See
+    <citerefentry project='man-pages'><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>
+    for more information. This function also internally caches the
+    returned ID to make this call a cheap operation.</para>
+
+    <para>Note that <function>sd_id128_get_boot()</function> always
+    returns a UUID v4 compatible ID.
+    <function>sd_id128_get_machine()</function> will also return a
+    UUID v4-compatible ID on new installations but might not on older.
+    It is possible to convert the machine ID into a UUID v4-compatible
+    one. For more information, see
+    <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+
+    <para>For more information about the <literal>sd_id128_t</literal>
+    type see
+    <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Return Value</title>
+
+    <para>The two calls return 0 on success (in which case
+    <parameter>ret</parameter> is filled in), or a negative
+    errno-style error code.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Notes</title>
+
+    <para>The <function>sd_id128_get_machine()</function> and
+    <function>sd_id128_get_boot()</function> interfaces are available
+    as a shared library, which can be compiled and linked to with the
+    <literal>libelogind</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    file.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+
+    <para>
+      <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>